The Chicago Bears have placed wide receiver Johnny Knox on the physically unable to perform list as he continues to rehab from back surgery. Knox said there is still no timetable for his full recovery. Knox suffered a fractured vertebra which reacquired surgery on December 18th in a game against the Seattle Seahawks. The Bears held their first training camp practice yesterday afternoon at Olivet Nazarene University in Bourbonnais. Chicago's first preseason game is on Thursday, August 9th in the Windy City against Peyton Manning and the Denver Broncos.